In some production processes, a web is transported past one or more devices that undertake manufacturing step(s). In other processes, the web itself is modified in some manner, such as by applying inks and/or coatings thereto.
In any such production processes, it is important that the web be precisely registered with the equipment undertaking the manufacturing step(s) so that the step(s) are undertaken correctly. Accuracy in the process direction is accomplished by accurate installation of production line components, and accurate control of web speed. Lateral positioning transverse to the process direction is accomplished by, among other things, accurately controlling the lateral web position. Most web steering or guiding systems that control lateral web position are intended for positioning a web as it enters a process from a source roll.
A known steering roll assembly sold by AccuWeb, Inc. of Madison, Wis., utilizes steering rolls mounted within a movable frame. A linear bearing system and linear actuator allow motion of the movable frame accomplishing the desired web steering function. The linear actuator is controlled by a control system that responds to measurements provided by a web edge sensor. Pivoting of the movable frame relative to an adjustable theoretical pivot point maintains a desired lateral web position. It has been found, however, that this steering roll assembly is not suitable for use in certain environments where space is limited due to constraints imposed by the process that is being undertaken. A more compact steering mechanism may also be required when adding this capability to existing equipment.
Most web steering or guiding systems are intended for positioning a web as it enters a process from a source roll. The guiding system corrects for a roll that is offset to one side or the other (a static error) or a roll that has lateral runout (uneven edge).